What is the importance of the Anna Karenina principle?

Answer 1

The Anna Karenina principle can be used to illustrate things, such as Jared Diamond used it for, like why so few animals have been successfully domesticated throughout history, as a deficiency in any one of a great number of factors can render a species undomesticable. Therefore all successfully domesticated species are not so because of a lack of any number of possible negative traits.

Successful risk ecological risk assessments are all alike; every unsuccessful ecological risk assessment fails in its own way. Tolstoy posited a similar analogy in his novel Anna Karenina: "Happy families are all alike; every unhappy family is unhappy in its own way." By that for a marriage to be happy, it had to succeed in several key aspects. Failure on even one of these aspects, and the marriage is doomed…the Anna Karenina principle also applies to ecological risk assessments involving multiple stressors.

Again, it is possible to fail in many ways (for evil belongs to the class of the unlimited, as the Pythagoreans conjectured, and good to that of the limited), while to succeed is possible only in one way (for which reason also one is easy and the other difficult -- to miss the mark easy, to hit it difficult); for these reasons also, then, excess and defect are characteristic of vice, and the mean of virtue; For men are good in but one way, but bad in many.

By studying the dynamics of correlation and variance in many systems facing external or environmental factors, we can typically, even before obvious symptoms of crisis appear, predict when one might occur, as correlation between individuals increases and at the same time, variance goes up… All well adapted systems are alike, all non-adapted systems experience maladaptation in their own way… But in the chaos of maladaptation, there is an order. It seems, paradoxically, that as systems become more different they actually become more correlated within limits.

"… for systems belonging to the singular part of the stability boundary a small change of the parameters is more likely to the send the system into the unstable region than into the stable region. This is a manifestation of a general principle stating that all good things are more fragile than bad things. It seems that in good situations a number of requirements must hold simultaneously, while to call a situation bad even one failure suffices"